Copyright The McGraw-Hill Companies.Inc.Permission required for reproduction or display. Chapter 14 Messenger RNA Processing I:Splicing Dr.David Spector/Peter Arnold,Inc
Chapter 14 Messenger RNA Processing I: Splicing
14.1 Genes in Pieces Consider the sequence of the human B-globin (β-球蛋白)gene as a sentence: This is bhgty the human B-globin qwtzptlrbn gene. Two italicized regions make no sense -( Contain sequences unrelated to the globin coding sequences surrounding them Called intervening sequences(插入序列，IVSs) - Usually called introns(内含子) Parts of the gene making sense -Coding regions - Eons(外显子) Some lower eukaryotic genes have no introns 14-2
14-2 14.1 Genes in Pieces ✓ Consider the sequence of the human b-globin (b-球蛋白) gene as a sentence: This is bhgty the human b-globin qwtzptlrbn gene. ✓ Two italicized regions make no sense – Contain sequences unrelated to the globin coding sequences surrounding them – Called intervening sequences (插入序列, IVSs) – Usually called introns (内含子) ✓ Parts of the gene making sense – Coding regions – Exons (外显子) ✓ Some lower eukaryotic genes have no introns
RNA Splicing Introns are present in genes but not in mature RNA Process of cutting introns out of immature RNAs and stitching together the exons to form final product is RNA splicing (RNA 接) 14-3
14-3 RNA Splicing ✓Introns are present in genes but not in mature RNA ✓Process of cutting introns out of immature RNAs and stitching together the exons to form final product is RNA splicing (RNA剪 接)
Splicing Outline CopyrightTe MeGraw-Hll Co Start of transcription √Introns are Intron 1 Intron 2 transcribed along Gene: Exon 1 Exon 2 Exon 3 with exons in the Transcription primary transcript Intron 1 Intron 2 √Introns are removed Primary transcript: Exon 1 Exon 2 Exon 3 as the exons are Splicing spliced together Mature transcript: Exon 1 Exon 2 Exon 3 14-4
14-4 Splicing Outline ✓ Introns are transcribed along with exons in the primary transcript ✓ Introns are removed as the exons are spliced together
Stages of RNA Splicing Messenger RNA synthesis in eukaryotes occurs in stages √First stage: Synthesis of primary transcript product -This is an mRNA precursor containing introns copied from the gene if present - Precursor is part of a pool of large nuclear RNAs- heterogeneous nuclear RNA(核不均一RNA,hnRNAs) √Second stage: -mRNA maturation - Removal of introns in a process called splicing 14-5
14-5 Stages of RNA Splicing ✓ Messenger RNA synthesis in eukaryotes occurs in stages ✓ First stage: – Synthesis of primary transcript product – This is an mRNA precursor containing introns copied from the gene if present – Precursor is part of a pool of large nuclear RNAs – heterogeneous nuclear RNA (核不均一RNA, hnRNAs) ✓ Second stage: – mRNA maturation – Removal of introns in a process called splicing